A wide variety of small fibers such as those used for making clothing and other woven and knit materials frequently are not tested for their tensile strength. Generally speaking, this is not such a critical parameter since usually there is such a multitude of fibers that they additively provide sufficient strength.
Other similarly dimensioned small fibers that are attracting a great detail of attention are the optical fibers. These may be only a few microns in diameter and serve to transmit vast amounts of data by optical means to expedite communications, data processing, etc. Just recently however, designers have begun to appreciate not only the data transfer capability but the considerable inherent tensile strength of these fibers so that they function not only as the information path but also as the strength member between a pair of stations.
These capabilities have not escaped the attention of marine scientists who wish to transfer information to and from undersea instrumentation packages. In addition to the huge data transfer capability and strength, the fibers have lower power requirements and are not influenced by external electromagnetic energy as are relatively heavier contemporary metallic conductors. Furthermore, the optical fibers are capable of transmitting certain types of data with less distortion as compared to the metallic conductors.
Because the fibers were intended to extend for several kilometers in certain instances, the exact limits of the fibers' strengths had to be determined. The hostile ocean environment with its currents, surge and wave action demands fibers that could withstand these continuing abuses. It became imperative that the fibers' strengths be known so that suitable modification, e.g. sufficient numbers of fibers, could be incorporated to provide a reliable data length.
Testing of individual ones of the fibers was difficult because with all of the known tensile load analyzers the fiber was clamped before the tensile forces were applied. Usually where this clamping occurred, additional spurious stresses were created which contributed to a premature failure. Wrapping the fibers about rods or tying them tended to create failure inducing torsional stresses. Either way, the pinching stresses or torsional stresses affected the actual value of the fiber's fatigue strength. Thus, there is a continuing need in the state-of-the-art for a fiber optic test apparatus that does not create failure inducing stresses so as to provide accurate indications of fiber strength.